Carby New PWK 21 Carby. Tuning? Low speed bogging?

[Hell on Wheels]

Just got my new 21mm PWK carb on my engine up from a 16mm RT. Upjetted pilot/idle jet from 37 to 41. Seems to idle fine. I have power until 1/4 throttle but I bog if I go more and WOT isn't effective at bringing the power back on. If I get enough speed, suddenly I'm able to pull beyond 1/4 throttle. Engine seems to run fine until about 7000 rpm where it bogs (probably from being too lean, but I am rarely up there; I think I need to do something with the power jet in regards to that). Anyone have a suggestion? Raise needle? Bigger main jet? I'm running 125 for the main up from stock 105.

 

[Street Ryderz]

Just got my new 21mm PWK carb on my engine up from a 16mm RT. Upjetted pilot/idle jet from 37 to 41. Seems to idle fine. I have power until 1/4 throttle but I bog if I go more and WOT isn't effective at bringing the power back on. If I get enough speed, suddenly I'm able to pull beyond 1/4 throttle. Engine seems to run fine until about 7000 rpm where it bogs (probably from being too lean, but I am rarely up there; I think I need to do something with the power jet in regards to that). Anyone have a suggestion? Raise needle? Bigger main jet? I'm running 125 for the main up from stock 105.

What pipe are you using? where does your pipe currently stage (hit)?

 

[Hell on Wheels]

What pipe are you using? where does your pipe currently stage (hit)?

Yz85 with about 3 inch header. It hit about 22mph ish on the old carb. I can go WOT after about 15mph

 

[Hell on Wheels]

Edit: 3 inches added to beginning length of pipe. All 1 inch steel pipe matching pipe ID

 

[Street Ryderz]

Yz85 with about 3 inch header. It hit about 22mph ish on the old carb. I can go WOT after about 15mph

Your pipe is staged to early at around 5k so that at 7k it falls off and goes lean becuase your no longer getting the exrta charge the pipe delivers.

 

[Hell on Wheels]

Your pipe is staged to early at around 5k so that at 7k it falls off and goes lean becuase your no longer getting the exrta charge the pipe delivers.

I understand that. Not my biggest concern right now. Tbh I would raise the exhaust port more if I needed higher than 7000 rpm anyway because exhaust duration is so miniscule. Which at that point I'm better off getting a smaller rear sprocket. Being able to handle hills at 30 mph now is great and is what I need.

My issue is power falling flat on it's face if the throttle is opened at low rpm.

 

[Jag]

Try down jetting further. I have a pwk with reeds and I needed to down jet it otherwise it would bog if I went WOT to quickly

 

[Hell on Wheels]

Try down jetting further. I have a pwk with reeds and I needed to down jet it otherwise it would bog if I went WOT to quickly

Downjet main or pilot? I thought I was running lean? Unless you mean upjet to 135 or bigger main which is what I thought was the solution.

 

[Jag]

Main deals with top end. Idle is around idle. Just try both larger and smaller on main and check the spark plug you can get the jets everywhere.

 

[Street Ryderz]

I understand that. Not my biggest concern right now. Tbh I would raise the exhaust port more if I needed higher than 7000 rpm anyway because exhaust duration is so miniscule. Which at that point I'm better off getting a smaller rear sprocket. Being able to handle hills at 30 mph now is great and is what I need.

My issue is power falling flat on it's face if the throttle is opened at low rpm.

If you can go to full throttle at 15mph that's 3,600 rpm and totaly normal,these are s**tty small engines and they don't wind up like a dirt bike (unload).Where a single speed setup is used load keeps the engine from accelerating quickly no matter what you do to the engine.& 7k is not unloaded you have 3-4k yet to go,Stock engines where guy's say they are doing say 35mph is just over 8k and sill not really reving up due to that load.The guys whom get to higher speeds are making more power to deal with the load and be able to spin it up to 10 even 11k so really your still along way off and having your pipe stage low means you will never get there,hills are always difficult at low rpm and the extra load leans the engine so most people set there bottom end up a bit fat(rich) so that hills or trying to force it to accelerate from down low doesn't make it to lean with a loss of power.